Light Absorption Enhancement and Laser-Induced Damage Ability Improvement of AA 6061 with Non-porous Alumina /CdSe@Al2O3/SiO2 Functional Gradient Films

Numerical calculations of ultraviolet to near-infrared absorption spectra by cadmium selenide quantum dots (CdSe QDs) doped in anodic aluminum oxide pores were performed using a finite-difference time-domain model. The height, diameter, and periodic spacing of the pores were optimized. Light absorption by the dots was enhanced by increasing the height and decreasing the diameter of the pores. When the height was less than 1 μm, visible light absorption was enhanced as the spacing was reduced from 400 nm to 100 nm. No enhancement was observed for heights greater than 6 μm. Finally, the optical mode coupling of the aluminum oxide and the quantum dots was enhanced by decreasing the pore diameter and periodic spacing, and increasing the height. Laser ablation verified light absorption enhancement by the CdSe QDs. The experiment verified the improvement of the laser-induced damage ability with wavelength of 355-nm after aluminum alloy 6061 coated with functional films, which was fabricated based on numerical calculations.

Europium doping of cadmium selenide (CdSe) quantum dots via rapid microwave synthesis for optoelectronic applications

UV-Vis spectroscopy and PL data show that structural incorporation of Eu3+ has an effect on the optical properties of CdSe QDs via energy transfer from host to dopant. This allows for QDs with tunable optical properties via numerous pathways.

Semiconductor Quantum Dots (CdX, X = S, Te, Se) Modify Titanium Dioxide Nanoparticles for Photodynamic Inactivation of Leukemia HL60 Cancer Cells

Titanium dioxide nanoparticles (TiO2-NPs) are highly efficient photosensitizers in traditional photodynamic therapy (PDT). The particle size of TiO2-NPs is small, only about 20 nm. However, the demands of ultraviolet light (UV) excitation feature shallow tissue penetration depth and may lead to severe tissue photon damage. Thus, in this research, TiO2-NPs are modified with semiconductor quantum dots (QDs) CdX (X = S, Te, Se) in various methods, such as ultrasonic, hydrothermal, sol-gel, aqueous phase, and hydrolysis precipitation. The transmission electron microscopy (TEM) images show that the size of CdSe-TiO2 is ranging from 6 to 14 nm. The ultraviolet-visible (UV-Vis) spectrum demonstrates that the CdX (X = S, Te, Se) modification can successfully extend the absorption range of TiO2-NPs into a different visible light region. CdSe QDs have the narrowest band gap compared with CdX (X = S, Te, Se) QDs. Visible light-activated CdSe-TiO2 nanocomposite shows the highest PDT inactivation efficiency toward HL60 cells compared with CdX-TiO2. The photogenerated carrier separation efficiency of CdSe-TiO2 nanocomposite is the highest shown in a fluorescence spectrum (FS). Furthermore, when conjugated with folic acid (FA), the prepared FA-CdX-TiO2 (X = S, Se) exhibits excellent cancer-targeting ability during PDT treatment. Optimum PDT efficiency of FA-CdSe-TiO2 indicates that photocatalytic and targeting ability is much higher than pure TiO2 and CdSe-TiO2. Our results provided a detailed investigation on the PDT performance of CdX (X = S, Te, Se) modified TiO2 and may act as a guide for further design of highly targeted performance visible-light response TiO2-NPs.

Rapid Detection of Dimethoate in Soybean Samples by Microfluidic Paper Chips Based on Oil-Soluble CdSe Quantum Dots

Given the imperative of monitoring organophosphorus pesticides (OPs) residues in the ecosystem, here a novel, facile and sensitive fluorescence sensor is presented for the rapid detection of dimethoate. In this work, surface molecularly imprinted polymer (SMIP) and microfluidic technology had been introduced to enhance the selectivity and portability of the described methodology. Oil-soluble CdSe quantum dots (QDs) synthesized in a green way were used as fluorescent material for the selective detection of dimethoate on the basis of static quenching and photoinduced electron transfer mechanism. Among many kinds of paper materials, glass fiber paper was used as the novel substrate of paper chip due to low pristine fluorescence and better performance when combining CdSe QDs. In the process of molecular imprinting, the interaction between several functional monomers and dimethoate molecule was investigated and simulated theoretically by software to improve the selectivity of the sensor. Consequently, the fabricated novel detection platform could effectively respond to dimethoate in 10 min with the concentration range of 0.45–80 μmol/L and detection limit of 0.13 μmol/L. The recovery in the spiked experiment soybean sample was in an acceptable range (97.6–104.1%) and the accuracy was verified by gas chromatography-mass spectrometry, which signified the feasibility and potential in food sampling.

Spontaneous Emission Enhancement of CdSe Quantum Dots Embedded in a Two-dimensional Photonic Crystal L3 Nanocavity

Two-dimensional photonic crystal nanocavities were designed to tailor cavity quantum electrodynamics. Enhancing the spontaneous emission of low-quality factor nanocavity with embedded CdSe quantum dots (QDs) emitters is the aim of this study. Low concentration layer of CdSe QDs was sandwiched between two layers of Si2 N3 membrane using plasma-enhanced chemical vapor deposition. The modification rate in spontaneous emission of L3 nanocavity up to 2.3-fold has been observed at 629.5 nm in compare to bare cavities. High field confinement in the sub-wavelength regime became an interest field for quantum electrodynamics applications and good platform to study light matter interactions.

Cytotoxicity Study of Cadmium-Selenium Quantum Dots (Cdse QDs) for Destroying the Human HepG2 Liver Cancer Cell

In this approach, Hepatocellular carcinoma (HCC) is originated from hepatocytes cell, which can spread several parts in the body. It increases the death rate of cancer patients and more common in men rather than female. Patients having large tumor are growing through expensive treatment such as chemotherapy, radiotherapy and surgery. Nano medicine such as nano-dimensional particles as well as quantum dots might be an alternative treatment with greater efficiency in cancer biology field. Modification of surface and chemical properties of cadmium groups quantum dots can easily penetrate into the cancer cell without harming normal tissues. Here, Cadmium-Selenium Quantum Dot nanomaterials (CdSe QDs) have been prepared in solution phase with 0.1 M concentration, which was potentially applied for the destroying of HepG2 cancer cell with 24 hour and 36 hour of incubation. Due to their size, surface properties, lower cost, QDs can easily attached to the cell and able to damage the cells more rapidly in vitro process. For cell death, gene expression and morphological changing analysis were completed MTT, Flow Cytometry, qRT-PCR assay. Finally, the cell deaths were observed by cell shrinkage, rupture of membrane and expression of apoptotic gene (Bcl2, Beta catenin, Bax) were positive comparing untreated HepG2 cell line.

Time-Resolved and Temperature-Dependent Fractional Amplitude Contributions to the Broadband Emission of CdSe Quantum Dots

The broadband spontaneous emission of excitons in CdSe quantum dots (QDs) is of great interest for the spectral imaging of living organisms or specific substances in the visible spectral region as well as in the biological optical window near the infrared spectral region. Semiconductor QDs that are near the bulk Bohr radius exhibit wide spectral tunability and high color purity due to quantum confinement of excitons within the dot boundary. However, with reducing dot size, the role of the surface-trapped state increases. The temperature-dependent photoluminescence (PL) confirms this with a ~3:1 emission intensity decrease from the surface-trapped state compared to the band edge. Large crystal irregularity, dangling ions, and foreign molecules can introduce new electronic transitions from surface-trapped states that provide broad spontaneous emission in the spectral region from visible to near IR in addition to the band edge emission. The time-resolved PL analyzed the fractional contributions of band edge, surface-trapped states, and possible intermediate trapped states to the broad spectral emission in order to characterize the CdSe QDs.

Effect of Copper Doping on Electronic Structure and Optical Absorption of Cd33Se33 Quantum Dots

The photophysical properties of Cu-doped CdSe quantum dots (QDs) can be affected by the oxidation state of Cu impurity, but disagreement still exists on the Cu oxidation state (+1 or +2) in these QDs, which is debated and poorly understood for many years. In this work, by using density functional theory (DFT)-based calculations with the Heyd–Scuseria–Ernzerhof (HSE) screened hybrid functional, we clearly demonstrate that the incorporation of Cu dopants into the surface of the magic sized Cd33Se33 QD leads to non-magnetic Cu 3d orbitals distribution and Cu+1 oxidation state, while doping Cu atoms in the core region of QDs can lead to both Cu+1 and Cu+2 oxidation states, depending on the local environment of Cu atoms in the QDs. In addition, it is found that the optical absorption of the Cu-doped Cd33Se33 QD in the visible region is mainly affected by Cu concentration, while the absorption in the infrared regime is closely related to the oxidation state of Cu. The present results enable us to use the doping of Cu impurity in CdSe QDs to achieve special photophysical properties for their applications in high-efficiency photovoltaic devices. The methods used here to resolve the electronic and optical properties of Cu-doped CdSe QDs can be extended to other II-VI semiconductor QDs incorporating transition-metal ions with variable valence.

Studies of Nucleation Phase of Mn-doped Cadmium-Selenide (CdSe) Quantum Dots Via Photoluminescence Spectroscopy

In this paper, we predict the nucleation phase of as-synthesized manganese (Mn) doped cadmium selenide (CdSe) quantum dots (QDs) at an intrinsic physical size of 3 (± 0.1 – 0.9) nm via photoluminescence (PL) studies. The nucleation phase was analyzed at temporal evolution (16, 46 and 90 mins) and temperature (210, 215 and 220 ºC) below the CdSe QDs reaction temperature (210 and 215 ºC) to it reaction temperature (220 ºC). The PL spectra`s observed to be against the QDs ripening behaviour of QDs since there are no prominent red-shift of PL spectra`s. However, the intensity of PL spectra`s shows to be varied with different temperatures and times.